The present invention relates to a variable valve timing control apparatus of an internal combustion engine, which variably controls open and closing timing of an intake valve and/or an exhaust valve of the engine in accordance with an engine operating condition.
A generally used vane type variable valve timing control apparatus is configured so that, in a state in which an application force by a hydraulic pressure does not act on the variable valve timing control apparatus upon stop of the engine, a vane member is positioned at a retarded angle side with respect to a timing sprocket with stability, due to an alternating torque occurring at a camshaft.
On the other hand, recently, various variable valve timing control apparatuses have been developed. One such variable valve timing control apparatus is disclosed in Japanese Patent Provisional Publication No. 2005-180378 (hereinafter is referred to as “JP2005-180378”). In JP2005-180378, in the case where the application force by the hydraulic pressure does not act on the variable valve timing control apparatus, the vane member is mechanically positioned at an advanced angle side with stability by a spring force of a torsion spring, or the application force is assisted in an advanced angle direction.
With regard to the torsion spring in JP2005-180378, its one end is bent in a radially outward direction and fixed in a retaining groove that is provided in a housing. The other end is bent in a radially inward direction and fixed in a retaining groove that is provided at the vane member.